1. Field of the Invention
The invention relates to the communication between two clients via a server in a network using OPC-UA.
2. Description of the Related Art
OPC Unified Architecture (OPC-UA) is a communication protocol and information model for communication between different automation components (devices).
OPC-UA is subject to a strict client-server model, i.e., servers provide information that is requested from the servers by clients. In this case, the communication between a client and a server is initiated by the client, i.e., communication always begins with the client and is therefore asymmetrical. If two components (devices) are intended to communicate with one another with equal rights (symmetrically), both must nowadays be the client and the server at the same time. There are restrictions on the transport layer, where clients and servers may be situated in the network. As a result, every client also cannot be made the server in every situation. In addition, simultaneous client and server functionality of communicating devices requires a greater outlay in terms of development and resources on both devices. This outlay is often not acceptable, particularly in the field, because the devices and networks used there are often relatively inefficient.